The present invention relates to a new and improved method of, and cutter head for, producing gears containing lengthwise crowned or cambered gear teeth. The invention further pertains to the use of the method and to gear teeth produced in accordance with the inventive method.
Generally speaking, the invention contemplates cutting the tooth flanks of gear teeth with a cutter head rotating about a cutter head axis and equipped with cutters having inner or internal cutting edges and outer or external cutting edges.
In Swiss Pat. No. 271,703, granted Nov. 15, 1950, there is disclosed a method and apparatus for cutting bevel gears possessing curved teeth, in accordance with a continuous generating method. The crown or camber of the teeth is obtained in that the outer or external cutting blades mutually have the same radial spacing from an axis of rotation of the tool, and the inner or internal cutting blades or cutters mutually possess the same radial spacing from such axis of rotation. This in effect means that the inner flanks of the gear teeth are produced by blades or cutters which possess a larger radial spacing from the axis of rotation than the blades or cutters by means of which there are produced the outer flanks of the gear teeth.
In Swiss Pat. No. 417,284, granted July 15, 1966, and the corresponding U.S. Pat. No. 3,218,931, there is disclosed a method and cutter head pair for the manufacture of lengthwise crowned or cambered teeth of a pair of bevel gears or hypoid gears possessing lengthwise curved gear teeth. The tooth crown is obtained by inclining the cutter head axis in a radial plane through the computation or operating pitch point of the tooth flank, with the same radii of the cutting edges of all of the blades or cutters with respect to the axis of rotation.
In Swiss Pat. No. 594,468, granted Sept. 15, 1977, and the corresponding U.S. Pat. No. 4,183,703, there is disclosed a method of fabricating a pair of spur gears. Here, the gear tooth crown or camber likewise is obtained by inclining the cutter head axis in a radial plane extending through the computation or operating pitch point.
With these prior art techniques for the fabrication of pairs of bevel gears, hypoid gears and spur gears, an increase in the cutting capacity or output is limited by virtue of the required type and quality of the load carrying image or load capacity of the tooth flanks.
Further constructions of gear cutting machines have been disclosed in U.S. Pat. Nos. 2,510,528; 2,881,665 and 2,932,239; and British Pat. No. 962,914.